Download Availability of Tachypleus gigas - International Journal of Fisheries

International Journal of Fisheries and Aquatic Studies 2015; 2(5): 334-336
ISSN: 2347-5129
IJFAS 2015; 2(5): 334-336
© 2015 IJFAS
www.fisheriesjournal.com
Received: 07-04-2015
Accepted: 05-05-2015
Siddhartha Pati
Horseshoe Crab research Unit,
Department of Bioscience &
Biotechnology, Fakir Mohan
University, Balasore-20, Odisha,
India.
Gobinda Ch. Biswal
Department of Zoology,
Sidheswar College, Amarda
Road, Balasore.
Bisnu P. Dash
Horseshoe Crab research Unit,
Department of Bioscience &
Biotechnology, Fakir Mohan
University, Balasore-20, Odisha,
India.
Correspondence
Bisnu P. Dash
Horseshoe Crab research Unit,
Department of Bioscience &
Biotechnology, Fakir Mohan
University, Balasore-20, Odisha,
India.
Availability of Tachypleus gigas (Müller) along the
river estuaries of Balasore district, Odisha, India
Siddhartha Pati, Gobinda Ch. Biswal, Bisnu P. Dash
Abstract
Populations of horseshoe crabs (Tachypleus gigas) along the northeast coast of India are under threat due
to destruction of the breeding beaches. In this present study the availability and habitat of that species
was surveyed. As per past report, Horseshoe Crabs were plenty available at Balaramgari beach along the
northeast coast of India, and they normally migrate towards the shore in large numbers coinciding with
the tidal height and grain size of the sediment and spawn in nests made in sand at Balaramgari beach. At
present very less nesting and breeding pairs were observed so far in that said beach. Many 25 m2 of areas
of the 3 estuary beaches were surveyed between January to December 2014 along the Balasore coast,
Odisha. Large numbers of nests and breeding pairs were encountered in Mahisali river mouth, Khandia
river mouth, where as very negligible number of crab was found at the earlier reported beach i.e
Balaramgari beach. Efforts should be made to protect their breeding beaches as well as to restore their
population by application of advance scientific technique like sea ranching.
Keywords: Tachypleus gigas, Horseshoe Crab, spawning pattern, sea ranching
1. Introduction
The Asian horseshoe crab, Tachypleus gigas (Müller), also known as Asian king crabs,
belongs to the family Limulidae. It is the only marine primitive invertebrate which is widely
distributed on earth. There are only four species of horseshoe crabs in existence in the world
today. These are Limulus polyphemus, Tachypleus gigas, Tachypleus tridentatus, and
Carcinoscorpius rotundicauda. These creatures are sometimes called “living fossils” because
they have changed little from their fossilized relatives; the earliest species identified is
approximately 450 million years old. They evolved from trilobites about 550 million years
ago, and keep similar shapes for more than 200 million years. They have been classified in
Phylum Arthropoda; subclass Xiphosura and phylo-genetically more related to Arachnida than
to Crustaceans [1-2].
In Asia, T. gigas are distributed from Bay of Bengal to South-West of Japan. The horseshoe
crabs in the Bay of Bengal are the widely distribution in Asia and their species distribution,
shapes and behaviors are very interesting. There are some reports about the distribution and
spawning activities of horseshoe crabs of Odisha and West Bengal in India [3].
T. gigas is one of the most important invertebrate animals which are used in researches as a
component of its blood to detect bacterial contamination in medical devices and drugs. This
species can usually be found from Indian shore to Southeast Asian region and disperse to the
South-western part of Lantau Island, Hongkong. It lives in sandy to muddy habitats [4-6]. In
India, some T. gigas co-exist with C. rotundicauda [7-8]. Along with other three species, T.
gigas is classified as either near threatened or data deficient [9]. Evidences from studies and
fishermen suggest that this species once commonly found in different habitats throughout Asia
is declining. Human disturbances have been attributed to the degradation and destruction of
spawning beaches in India.
This species uses the intertidal zones of Odisha coast, associated with estuaries and creeks for
breeding. This is due to the favorable conditions such as beach characteristics, estuaries, creek
environment and suitable sand grain size at the breeding beaches. [10] Among the four species
of king crabs, T. gigas is comparatively less studied. Very limited information is available on
this species about its reproductive biology and population dynamics.
The Bay of Bengal, Odisha coast has a commercial fishery which uses king crabs for fertilizer
and animal feed but it ceased in the recent years. However at present there is large fishery
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International Journal of Fisheries and Aquatic Studies
activity on various marine organisms in the Odisha coast.
Human activities nevertheless threaten the crab’s survival in
various parts of the world. Beach development and shoreline
modifications are some of the important reasons which prevent
the crabs from reaching spawning areas. Oil spills from barges
or tankers have been reported to pose threats to breeding and
young ones. Although many efforts have been taken in various
countries to increase the population of the species by
implementing better management practices, the population is
not showing immediate increase. The crabs do not breed until
nine to ten years and this is another reason for the reduced
population size of the species. There have been numerous
studies concerning the general biology and life history of T.
gigas, information concerning its status and population
biology is not sufficiently known. As the demand of the
species intensifies from different user groups, information
about its status becomes increasing necessary. There are
concerns that the population is declining and for any future
management, an accurate data on the population biology of the
species is very essential.
2. Material and method
2.1 Study sites
Balasore district is located in the northeast of the state of
Odisha and lies between 21° 3' to 21° 59' north latitude and
86° 20' to 87° 29' east longitude. The average altitude of the
district is 19.08 m and has a total area of 3634 km2. The
coastal belt is about 81 km wide and shaped like a strip. In this
region, sand dunes are noticed along the coast with some
ridges. This region is mostly flooded with brackish water of
estuarine rivers which is unsuitable for cultivation. Shrimp
culture and salt manufacturing units are also developing in this
area recently. Two important rivers namely Budhabalanga and
Subarnarekha and many sub rivers pass through this district
from west to east before surging into the Bay of Bengal and
make an estuary which is suitable for this horseshoe crab. Out
of them Mahisali estuary, Balaramgarhi, Khandia estuary was
selected for the survey under Balasore coast of Bay of Bengal.
Mahisali estuary sea beach is located at 21°24'35.97"N and
86°58'43.02"E in Balaore district near the mouth of Mahisali
Estuary River and surrounding areas. It is about 5 km away
from Chandipur. Balaramgarhi sea beach is located at
21°28'10.06"N and 87° 3'37.00"E in Balasore district near the
mouth of Balaramgarhi Estuary River and surrounding areas. It
is about 6 km away from Chandipur. Khandia estuary sea
beach is located at 21°19'1.65"N and 86°53'32.99"E in
Balasore district near the mouth of Khandia estuary river and
surrounding areas. It is about 15 km away from Chandipur.
m2 (1m width x 25m long) in each site to increase the area
covered by the survey. A gap of 10 m was maintained between
two transects.
Spawning survey was carried out regularly twice a month,
coinciding with full and new moon phases from January to
December 2014. The samples were collected one hour prior to
and one hour following the predicted high tides except under
extreme weather conditions. Since the breeding activity was
more pronounced in the daylight high tide than the night tides
for T. gigas [11], in our present study, we restricted all our
observations during day light hours at the highest high tides of
full or new moon. All animals within transects were counted
and recorded the number of single males, single females, pairs
(female and amplexed male), females with amplexed males
and satellite males.
3. Result
In our study, the population of T. gigas has been found
throughout the year, though the breeding season of this species
is found to be restricted. The spawning density of T. gigas
varied between high tide of full moon and low tide of new
moon.
At Balaramgadi estuary beach, during 2014, a total of 12
males/transect (=25 m2) and 10 females was observed in new
moon while a total of 06 males and 07 females were observed
during full moon. The total number of crabs arrived during the
year 2014 were 22 during new moon and 13 respectively
during full moon (Fig-1). At Mahisali estuary beach, during
2014, a total of 16 males/transect (=25 m2) and 18 females
were observed in new moon while a total of 14 males and 18
females were observed during full moon . The total number of
crabs arrived during the year 2014 were 34 during new moon
and 32 respectively during full moon (Fig-2). At Khandia
estuary beach, during 2014, a total of 33 males/transect (=25
m2) and 34 females were observed in new moon while a total
of 30 males and 35 females were observed during full moon.
The total number of crabs arrived during the year 2014 were
67 during new moon and 64 respectively during full moon
(Fig-3). The population of T. gigas has been found throughout
the year, though the breeding season of this species is found to
be restricted from March to September. The spawning density
of T. gigas varied between high tide of full moon and low tide
of new moon.
2.2 Survey on spawning density
To estimate the density of spawning population of T. gigas,
surveys were made in the above mentioned three estuaries
during Jan 2014-Dec-2014 using quadrate/transect sampling.
To standardize the minimum area to be surveyed, we
examined several protocols for the survey adopted by various
workers. Initially the quadrate size was restricted to 1m x1m
and the number of quadrat in each site was 25 (twenty five)
and randomly laid to assess the spawning population.
However, the data collected from these quadrates showed a lot
of variations and we missed many a times to record the
availability of T. gigas from the small size of the quadrate.
Since the spawning density was observed to be relatively
lower compared to many other studies reported, instead of
using quadrates, we laid out four transects each measuring 25
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Fig 1: Month wise variations and Population density (mean
number/25m2) of T. gigas population during new moon and full
moon at Balaramgadi estuary.
International Journal of Fisheries and Aquatic Studies
Fig 2: Month wise variations and Population density (mean
number/25m2) of T. gigas population during new moon and full
moon at Mahisali estuary
Fig 3: Month wise variations and Population density (mean
number/25m2) of T. gigas population during new moon and full
moon at Khandia estuary
4. Dicsussion
Horseshoe crab were plenty available at Balaramgari beach
Along the northeast coast of India, and they normally migrate
towards the shore in large numbers coinciding with the tidal
height and grain size of the sediment and spawn in nests made
in sand at Balaramgari beach [13] but this survey shows that the
habitat has almost shifted to Balaramgari estuary to near
estuary where less human activity are there in same district
Balasore. Horseshoe crabs were incidentally caught largely by
trammel net used for prawn fishing, mechanized trawler nets,
monofilament gill netting on the mudflats and beach shore
seine [12]. Currently, the availability of horseshoe crabs (T.
gigas) are restricted to smaller areas of coast of Balasore. In
this connection, it is suggested to declare those remaining
breeding part of horseshoe crabs as a conservation reserve.
Efforts should be made to protect their breeding beaches from
destruction and environmental degradation. Environmentalists
should ensure regular planting of trees to control beach
erosion, ban the removal of sand gravel for construction
purposes, Restriction of trawler and local fisher community in
that breeding beaches. Further attempt can be made to increase
the horseshoe crab population by the application of advance
scientific technique and conserve the valuable creature from
the verge of extinction.
5. References
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9. IUCN (International Union for Conservation of Nature)
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11. Chatterji A, Vijayakumar R, Parulekar AH. Spawning
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5. Acknowledgements
All the authors are thankful to Vice Chancellor, Fakir Mohan
University, Balasore for the facilities and encouragements.
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